Field of the Invention
The present invention relates to a photoacoustic apparatus which uses a photoacoustic effect to acquire information on a subject (hereinafter, called subject information).
Description of the Related Art
A technology (Photo Acoustic Tomography or PAT hereinafter) which acquires functional information on a living body using light and ultrasound has been proposed in the past.
When a tissue of a living body is irradiated with pulsed light such as visible light and near-infrared light, a light absorbing substance, particularly a substance such as hemoglobin within blood within the living body absorbs energy of the pulsed light and instantaneously expands. As a result, photoacoustic waves (typically ultrasound) are generated. This phenomenon is called a photoacoustic effect, and PAT visualizes information of the biological tissue by measuring the photoacoustic waves. Visualizing a light energy absorption density distribution (density distribution of a light absorbing material within a living body which is a source of photoacoustic waves) as information of a biological tissue allows imaging of an active neovessel due to a cancer tissue. A light wavelength dependency of the occurring photoacoustic waves may be utilized to acquire functional information such as an oxygen saturation of blood.
The PAT technology allows non-exposure and non-invasive diagnostic imaging because it uses light and ultrasound for imaging biological information and achieves a large advantage in view of burdens on a patient. Therefore, use of the technology is expected for screening of a breast cancer and an early diagnosis, instead of an X-ray apparatus which is difficult to be used for repetitive diagnoses.
Japanese Patent Laid-Open No. 2012-179348 discloses a technology which acquires wide-range subject information by mechanically scanning a probe including a plurality of acoustic wave receiving elements arranged at different positions on a hemispherical surface. The direction of reception of the acoustic wave receiving elements arranged on the spherical surface are caused to point to a predetermined region to visualize the predetermined region with a high resolution. The position of the hemispherically shaped probe, that is, a predetermined region which may be visualized with a high resolution, may be mechanically scanned so that a wide range subject region may be visualized all over with a high resolution.
The apparatus disclosed in Japanese Patent Laid-Open No. 2012-179348 requires storage of a reception signal output from a transducer in a memory when probes are positioned at a plurality of positions. On the other hand, reduction of the amount of data of a reception signal to be stored in memory has been demanded.